All eyes were on Jack Brinkley Cook while Nina Agdal was away

Jack Brinkley Cook was a sitting duck out east this weekend, where all eyes were on the 23-year-old socialite while his supermodel girlfriend Nina Agdal girlfriend was away.

“He has become a Hamptons heartthrob,” according to one party goer at Saturday night’s St. Barth Hamptons Gala benefiting the Bridgehampton Museum

The event was hosted by Cook’s model mom, Christie Brinkley, but a source at the events said that single women at the party literally couldn’t get enough of Cook. He remained largely insulated by a pack of male pals throughout the evening.

“He was being good, coming and going with a guy pack and not too close to any one girl,” according to that source. “(Agdal) didn’t have to worry about him misbehaving like his infamous father.”

The elder Cook, a famed architect, in 2008 had a fling with his 19-year-old assistant. He and Brinkley ended their 12 year marriage a short time later.

Before the party started, Agdal, 26, posted an Instagram picture of herself kissing her 23-year-old beau in a pool.

“Can’t wait for this guy to get to Dane Land,” the Danish model captioned the photo.

The two have recently developed a reputation for PDA. Last month, a paparazzi pic of the pair making out rather passionately in a Montauk nightclub found its way to the Internet. Vanity Fair’s wrote about it under a screaming headline reading “Nina Agdal and Jack Brinkley-Cook Learn The Hard Way That What Happens in Montauk, Stays in Tabloids Forever.”

Cook’s mom was turning heads at the party too — and she somehow defied Mother Nature.

“It was raining like crazy and she was wearing all white,” according to the party source. It was as if an occult hand had delivered the 64 year old model through the storm.

“It didn’t dampen the party,” said that source. “She looked perfect.”

Brinkley arrives at the party with “Orange is the New Black” actress Rebecca Knox, them chatted with Social Life magazine publisher Devorah Rose once inside. Rose put Brinkley on the mag’s cover last week.

The “Uptown Girl” earned her keep at the fundraiser.

“She hopped behind the bar and was pouring glasses of her Belissima Wine for about 40-minutes,” that source said.